And the plant continues to release radiation to this day, despite efforts to contain the leaking.

“There have also been reports of declines in other species”

Nikolaos Evangeliou

Now a study from the Norwegian Institute for Air Research has revealed the true extent of the global impact.

Lead author Nikolaos Evangeliou told New Scientist magazine: "What I found was that we got one extra X-ray each."

According to the NHS website, people exposed to X-rays face the risk of developing cancer "many years or decades later."

And though the risk is small – Mr Evangeliou says “we don’t need to worry” – it underlines the scale of the Fukushima disaster.

Inside Japan's CHERNOBYL: the ghost town abandoned after Fukushima meltdown

Namie is a town five miles away from the Fukushima nuclear power plant. It was evactuated shortly after the reactor went into meltdown in 2011. Five years later, people slowly started to return to the town.

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Bloomberg via Getty Images

A doll sits inside an abandoned house

The dose was calculated using data from a global network of measuring stations monitored by the Comprehensive Test Ban Treaty Organization.

"More than 80% of the radiation was deposited in the ocean and poles, so I think the global population got the least exposure," said Mr Evangeliou.

Most people got 0.1 millisievert of extra radiation from the Fukushima disaster – though the figure was five times higher in Japan.

GETTY

DESTROYED: Photos of a hole inside Fukushima's destroyed reactor two

In comparison, the average of annual dose from background radiation for people in the UK is around 2.7 millisieverts a year.

But the effect on wildlife is worst – radiation has already been linked to bird population decline near Fukushima.

"There have also been reports of declines in other species such as insects and mammals," said Mr Evangeliou.